Friday, November 02, 2007

I have wondered before if economists do anything other that testpeopleplaying the ultimatum game. Now it looks like biologists are moving in on the economists' turf.

To find out if chimpanzees share this sense of fairness, Keith Jensen and his colleagues at the Max Planck Institute for Evolutionary Anthropology, in Leipzig, designed a way for chimps to play the ultimatum game. Their version started with a pair of trays far from the players' cages. Each tray had ten raisins divided in different ways between two pots—say eight and two, or five and five. One chimp was allotted the role of proposer. He could choose one of the trays, pulling it by way of a rope just halfway to the cage. The other, the responder, could then choose to pull on a rod, bringing the tray close enough for both to get the raisins, one pot for each. If the responder chose not to pull the tray closer within a minute, the offer was considered rejected, and the game concluded.

The result, which Dr Jensen reports in Science, is that chimps are simply rational maximisers—Pan economicus, if you like. Though proposers consistently chose the highest possible number of raisins for themselves, responders rarely rejected even the stingiest offers.

Chimpanzees act more like textbook Homo economicus than humans, who would have thunk? Any reason why?

This is a telling outcome. A number of researchers in the field of human evolution think that a sense of fairness—and a willingness to punish the unfair even at some cost to oneself—is humanity's “killer app”. It is what allows large social groups to form. Without it, free-riders would ruin such groups, because playing fair would cease to have any value.

Hmm, so not being a “rational maximiser” was the key to humans success? That doesn't bode so well for economics.

How else do chimps differ from humans?

The human participants in Dr Hauser's experiment were allowed to choose a preferred food, such as raisins or chocolate. The chimpanzees were simply offered grapes—which they usually like. Otherwise the experimental conditions were identical. The choice was between one unit of goodies immediately and three after two minutes. Chimpanzees were nearly four times more likely to wait for the big reward than humans were.